Sunday 8 July 2012

Stefano Mancuso: Evolution of Plant Intelligence

Unfortunately, Professor Mancuso had to cancel his trip in the last minute for personal reasons, but here is a TED video that gives the flavour of his work. Comments are still invited, on his video and on the linked readings. It is possible (though not certain) that Professor Mancuso will reply to the comments.

      Abstract: Intelligent behavior is a complex adaptive phenomenon that has evolved to enable organisms to deal with variable environmental circumstances. Maximizing fitness requires skill in foraging for necessary resources (food) in competitive circumstances and is probably the activity in which intelligent behavior is most easily seen. Biologists suggest that intelligence encompasses the characteristics of detailed sensory perception, information processing, learning, memory, choice, optimisation of resource sequestration with minimal outlay, self-recognition, and foresight by predictive modeling. All these properties are concerned with a capacity for problem solving in recurrent and novel situations. I will review the evidence that individual plant species exhibit all of these intelligent behavioral capabilities but do so through phenotypic plasticity, not movement. Furthermore it is in the competitive foraging for resources that most of these intelligent attributes have been detected. Plants should therefore be regarded as prototypical intelligent organisms, a concept that has considerable consequences for investigations of whole plant communication, computation and signal transduction.
    It should not be surprising that neuronal computation is not limited to animal brains but is used also by bacteria and plants. It is generally assumed that brains and neurons represent late evolutionary achievements which are present only in more advanced animals. But recent data suggest that our understanding of bacteria, unicellular eukaryotic organisms, plants, brains and neurons, rooted in Aristotelian philosophy is flawed. Neural aspects of biological systems are obvious already in bacteria and unicellular biological units such as sexual gametes and diverse unicellular eukaryotic organisms. Altogether, processes and activities thought to represent evolutionarily 'recent' specializations of the nervous system may be ancient and fundamental cell survival processes.

      Mindless mastery - Nature 2002
      Aspects of Plant Intelligence - Annals pf Botany 2003
      Plant intelligence - Naturwissenschaften 2005
      Green plants as intelligent organisms - TRENDS in Plant Science 2005
      Plant Neurobiology as a Paradigm Shift Not Only in the Plant Sciences
      Plant neurobiology: no brain, no gain? - TRENDS in Plant Science 2007
      Response to Alpi et al.: Plant neurobiology: the gain is more than the name - TRENDS in Plant Science 2007
      Response to Alpi et al.: Plant neurobiology - all metaphors have value - TRENDS in Plant Science 2007
      Reflections on 'plant neurobiology' - BioSystems 2008
      Plant neurobiology: from sensory biology, via plant communication, to social plant behavior - Cognitive Process 2009
      Spatiotemporal dynamics of the electrical network activity in the root apex - Proceedings of the National Academy of Sciences 2009
      Deep evolutionary origins of neurobiology - Communicative & Integrative Biology 2009

Comments invited


  1. I would have very much like to see this conference. I thought the TedTalk video was very very interesting. We do often underestimate the adaptative capacities of plant.

    1. The accelerated images showing plant development over time also pointed out that we are usually not aware of the complexity of our familiar environment. The transitions and differences highlighted between day and night plants behaviours were interesting. So was the complexity of their movements.
      Plants have developed the capacity of surviving in moving environments by integrating this changing information with the evolutionary constraint of being rooted. We could learn a lot from their complex sensory mechanisms.

      Audrey Doualot

    2. Such a shame that Stefano Mancuso was not able to come. Tackling the question of consciousness through plants is so rare but so fundamental when we want to push the reasoning of consciousness further as we did so far in this summer school. The TED talk was very inspiring and is worth to be watched.

  2. To see more on the behavior of plants, there is also this longer (44 min) documentary:

    Roxanne Deschênes

  3. Both the TED and the CBC documentary point out the apparent complexity in the 'behaviour' of plants. I agree that the patterns of the root branches growing and looking for nutrients and the target-specificity of the daughter parasite plants are surprising/interesting. But I do not think that they show anything more than an automatic response. Roots grow towards a greater density of nutrients in the soil. The daughter plants picked up on the volatile chemical cues from the tomato plants. These instances just mean that plants are highly sensitive to these cues and respond by growing towards them. The same can be said about the sunflower moving to face the sun. Sure they are 'smart' plants as in they are pretty adaptive but do they experience things? What I was interested in, though, is the action potentials measured in the roots...

    1. You are probably right. But why are organisms responses not likewise just automatic responses -- even at Turing scale? (They are not; we know that. But why not? The answer cannot be just a just-so story.)

  4. Where will we ever draw the line? What is NOT conscious? We all agree that inanimate objects are not conscious (Or do we...Dr. Harvey would disagree). A plant seems inanimate to most lay observers. But, as in Dr. Mancuso's TED talk, accelerated plant behavior shows movement, simply at a scale that we, as a human beings, are not usually attuned to. Now, because we know plants move, are we not more likely to allow for some form of plant consciousness? If so, it would seem that movement is an implicit criteria for our attribution of consciousness. Why? Because this is how we attribute consciousness to other humans as well - by observing patterns in their behavior (which are made up of movements) and by comparison with our own patterns of behavior we know result from being in certain mental states.

    Suppose we look at planetary movement. The solar system certainly moves. Is it conscious? Of course not! But why not? I am not saying that movement is the sole criteria we use to attribute consciousness - far from it - but I am having difficulty understanding what exclusion criteria for consciousness remain if plants are deemed conscious.


      Don't tie yourself up in knots. Until further notice, biological organisms on earth are conscious (feel): Tempests and teapots do not. I think (hope!) plants don't. And whether an organism feels anything at all or not (ever) is all or none: It either does or it doesn't. Doing is "movement," and it is indeed via doing (hence movement) that we can mind-read whether or not something feels (that's the Turing Test).

      But none of that is the hard problem: The hard problem is explaining why and how organisms feel, rather than just do.

    2. Thank you for your response Dr.Harnad. So does it not matter which organisms do feel, and which do not? It seems difficult to disentangle the hard from the easy at these stages, since attribution of feeling is done through observation of doing. And I am tempted to think that in order to tackle the hard problem, it would be useful to have some agreement over which organisms feel. I would also feel more comfortable saying that plants do not feel. But when, in the phylogenetic tree, do we start attributing feeling? We could simply say that all animals feel. But that answer is dissatisfying, at least for some. For instance, sponges are animals, but I have a hard time thinking they feel. Perhaps I am wrong though. Perhaps attempts to solve the hard problem need not be informed by these attribution criteria.


      The hard problem is explaining how and why those organisms that do feel, feel.

      The other-minds problem is determining which organisms feel. I would say that down to invertebrates it's evident enough (even if not certain) that they feel. With sponges, plants, micro-organisms, and unicellular organisms the other-minds problem definitely gets harder -- though it doesn't become the "hard" problem.

      The two problems are not unrelated, but it is a mistake to think they are the same problem.

    4. This was a really interesting and enlightening talk. But like Dr. Harnad alludes, I think that complexity of "behaviour" does not equate to consciousness. This talk also should remind us of the dangers of attributing consciousness to others based on our subjective and consequently anthropocentric concept of consciousness; just because a plant exhibits behaviours that seem analogous to our own sleep states, this does not mean that they experience the entrance to and exit from sleep states as we do. There was no evidence of any subjectivity. I can't yet imagine the adaptive advantage of subjectivity as opposed to strictly reactionary responses for a plant, which has little need for internal representation and contextualization for the behaviours exhibited by plants.

  5. This topic really intrigues me and I'm disappointed that we didn't get to see Mancuso present (although I hope everything is okay with him!). This kind of topic really brings up some interesting ethical questions for me - how do we decide/define which beings are killable? Are we only okay with eating plants because they are further removed from our state of being, or do they not have consciousness/feeling and therefore it is okay that we eat them?


      I hope plants don't feel. If they do, it does not follow that we should all starve ourselves to death.

      The moral argument for veganism is that one can live healthily without eating animals, so if we insist on killing them for food, we are doing it for the taste, not out of necessity.

      And for those of us who would like to think of ourselves as decent and humane, that is not a very decent or humane way to live and act.

      But if plants did feel, it would mean that vegans still have to eat them, not needlessly for the taste, but necessarily, to survive.

      But, please, let us keep things in proportion. There are billions of animals, about whom we can be sure they feel, being bred and butchered daily, just for our tastes. We first need to fix that obvious abomination, before beginning to ponder the far-fetched possibility that plants, too, might feel.

      That said, when I look at what used to be a forest, clear-felled for lumber -- or even see a large, noble tree, chopped down, I know we are doing something terrible, if not to a feeling creature, then to a noble and beautiful environment. (Some will reply that that is only a matter of taste -- and if trees really don't feel, I suppose they are right...)

  6. What empirical evidence does Dr. Mancuso have for claiming that root apexes work in networks in order to share information? In the TED talk, he does not provide any data which shows that they do in fact interact with each other and that they share substantive information in a way that could justify ascribing them abilities to communicate and to play, as Dr. Mancuso does.

  7. Why aren’t plants conscious? What criteria are they missing?

    Perhaps a question that could help would be to ask why plants didn't develop/evolve consciousness? What makes them different from other biological/living beings (although having developed such complex and adaptive behaviour)? Does anyone think that plants could/will ever develop consciousness?
    As Dr. Harnad mentioned whether plants have consciousness or not is not the hard problem and does not explain why and how organisms feel, but maybe in understanding why it did not evolve in certain organism, such as plants, might help us understand why it did in others.

    Thinking of Dr. Floreano’s evolved social robots and comparing their ‘level’ of consciousness or of not being conscious yet, would something have to be biological to have consciousness or is that just part of our bias as living beings? Would we be quicker to accept a plant as having evolved consciousness than a robot?
    I will have to look this up , but has plants' complex sensory systems and behaviours ever been modelled in robots?

    1. Interesting questions. Like you, it brings up a question like: Can consciousness exist without the organism being alive?

      Is life a pre-requisite for consciousness? If so, why?
      What is it about life that is important?


      Actually, the question with plants does not seem to be whether life (i.e., being a biological organism) is necessary for feeling (it probably is) but whether it is sufficient for feeling (i.e., do all biological organisms feel?).

      Of course, if a Turing robot (T3) is possible, and feels, then being a biological organism is not even necessary for feeling. (To argue that a feeling robot is not "alive" is as vacuous as to argue that an organism is not a "machine.")